This invention relates to optical signal assignment in an optical wavelength division multiplexing (WDM) network and, more particularly, to an access control arrangement including a dynamically assignable optical signal modulator and demodulator apparatus for use in such a WDM network.
In a communication network, optical links are used to interconnect switches, routers, and multiplexers. On each optical link, a number of wavelengths are supported using Wave Division Multiplexing (WDM). At different times it is necessary to increase and/or reduce the number of wavelengths needed to provide the desired communication services over the optical links. The need for changing the number of assigned wavelengths is due to variation in traffic demand on each link between two nodes, or among various origination/termination switches/routers. Furthermore, it is desirable to eliminate the need for packet buffers at routers in the network as much as possible in order to improve network performance.
In the above-described applications, what is needed is a method for adjusting the number of wavelengths based on traffic demand at originating/terminating routers as well as traffic demand on the links between the routers.
Our inventive method and apparatus solves the above needs by effectively responding to variations in network traffic by dynamically assigning the number of wavelengths at originating and terminating optical signal access apparatus. A controller of an optical signal access apparatus monitors network traffic by checking the occupancy level of a data buffer and determines therefrom the number of optical signals that should be allocated to handle the network traffic from that buffer. When the optical signal access apparatus is part of a router it can be used to control traffic at the router as well as on the links between the routers of an optical network.
More particularly, an optical signal access apparatus is disclosed comprising (1) a data buffer for storing received electrical data packets and for outputting electrical data packets; (2) a plurality of optical signal modulators, each for modulating a different optical signal using the outputted data packets from the buffer; (3) a switch, responsive to a control signal, for switchable connecting the outputted data packets to one or more of the plurality optical signal modulators; and (4) a controller for checking a data packet occupancy level of the buffer and, in response thereto, sending said control signal to the switch indicating a number of the plurality optical signal modulators to be assigned to receive the outputted data packets from the data buffer.
According to another aspect of the invention, the optical signal access apparatus may be part of an optical router including (1) an optical switch having a plurality of inputs for receiving modulated optical signals from the optical modulators and for switchable connecting them to a plurality of outputs; (2) a plurality of wavelength interchangers connected to the outputs of the optical switch, each wavelength interchanger for changing a received optical signal to a selected one of a group of wavelengths in response to a control signal from the controller; and (3) an optical multiplexer for multiplexing together the selected wavelengths outputted from the interchangers into a wavelength division multiplexed (WDM) optical signal.
According to another aspect of the invention, the optical modulators are wavelength selectable lasers having wavelengths that are selected in response to a control signal from the controller and the optical signal access apparatus is part of an optical router including an optical multiplexer for multiplexing together the selected wavelengths outputted from the wavelength selectable lasers into a wavelength division multiplexed (WDM) optical signal.
According to yet another aspect, the optical signal access apparatus also includes (1) a plurality of optical signal demodulators, each for demodulating a different received optical signal into electrical data packets; (2) a second switch, responsive to a second control signal, for switchable connecting electrical data packets outputted from one or more of the plurality optical signal modulators to a second data buffer; (3) the second data buffer used for storing received electrical data packets and for outputting electrical data packets; and (4) a second controller responsive to a received third control signal for sending the second control signal to the second switch indicating the number of optical signal modulators to be connected to the second data buffer.
When the optical signal access apparatus is part of an optical network including a plurality of routers, the controller is responsive to communications with those routers for determining the number and wavelengths of optical signals assigned to the optical signal access apparatus.